Cut off by rising floodwaters, ecologist Dr Eleanor Harper is stranded in the heart of Black Fen—a place that hums with rot and remembering. Each night, the marsh draws closer. Each night, something stirs in the reeds. It watches. It waits. And when it comes, Celia will be offered a choice. In the drowning dark, she will learn what it means to be claimed by the marsh—and what must be given in return.